Originally Posted by GTM_Challenge
As with any aftermarket part, warranty issues are different dealership to dealership. We haven't had any issues on our shop car, but that's not to say you won't.
There are laws out there to protect the consumer with their rights to aftermarket parts vs. warranty work, but I won't go into them here.
That's the normal line of reasoning. I was curious as to how BMW has reacted in the past to these types of mods. Technically, they have to prove that the issue with your car was caused by the mod (as far as i know) to deny your warranty claim. They can't legally deny your malfunctioning sunroof because you have an intake, but if your car has other issues with the engine, who's to say they wont see a mod and simply say it was the culprit. That's when the lawyers come to play, which few want to bother with (and I think car companies/dealers bank on).
See this alot with the mustang community. As he said, it varies from dealer to dealer also. Some are looking to void any warranty claim if they see a mod while others are much more 'friendly' to modified cars.